Cell biology

mTORC1

Biology

Lipopolysaccharide

Endocrinology

Signal transduction

Macrophage polarization

Biochemistry

Caloric theory

Computational biology

Immunology

Immune system

In vitro

Macrophage

Inflammation

Lipid metabolism

Gut flora

Innate immune system

TLR4

PI3K/AKT/mTOR pathway

Cell Metabolism

Caloric restriction (CR) stimulates development of functional beige fat and extends healthy lifespan. Here we show that compositional and functional changes in the gut microbiota contribute to a number of CR-induced metabolic improvements and promote fat browning. Mechanistically, these effects are linked to a lower expression of the key bacterial enzymes necessary for the lipid A biosynthesis, a critical lipopolysaccharide (LPS) building component. The decreased LPS dictates the tone of the innate immune response during CR, leading to increased eosinophil infiltration and anti-inflammatory macrophage polarization in fat of the CR animals. Genetic and pharmacological suppression of the LPS-TLR4 pathway or transplantation with Tlr4-/- bone-marrow-derived hematopoietic cells increases beige fat development and ameliorates diet-induced fatty liver, while Tlr4-/- or microbiota-depleted mice are resistant to further CR-stimulated metabolic alterations. These data reveal signals critical for our understanding of the microbiota-fat signaling axis during CR and provide potential new anti-obesity therapeutics.

Functional Gut Microbiota Remodeling Contributes to the Caloric Restriction-Induced Metabolic Improvements